How far away the object is by timing the echo?

To calculate the distance of an object based on echo timing, measure the time it takes for a sound wave to travel to the object and back. Divide this time by 2 to get the one-way travel time. Then multiply the one-way travel time by the speed of sound in the medium the sound is traveling through (approx. 343 m/s in air at room temperature) to find the distance to the object.